Creatine: what it is, how it works, and who should take it

With proven performance-enhancing effects, creatine is widely recognised as one of the most effective and well-researched supplements for improving high-intensity exercise and increasing lean muscle mass [1,2].

While it’s entirely possible to get creatine naturally from your diet (mainly through meat and fish, if you eat them), supplements have grown in popularity among athletes and everyday gym-goers looking to push their performance further. If you’re a vegetarian or vegan, you may benefit even more from supplementing.

In this blog, we look at:

• What is creatine?
• How do supplements work?
• Three key benefits
• What to look for in a supplement
• Creatine and your blood test results

 

What is creatine?

 

Creatine is a naturally occurring compound stored in your muscles and brain. It helps your body produce energy quickly, especially during short bursts of high-intensity activity like sprinting, weightlifting, or HIIT.

Your body produces creatine in the liver and kidneys, but you also get it through food (mostly red meat and fish) because of this, vegetarians and vegans tend to have lower stores, which can impact performance and recovery. 

Quick facts:

• 95% of your body’s creatine is stored in muscle [3].
• It works by helping regenerate ATP, your body’s primary energy source.
• It may support both physical performance and brain function.
• Supplementing is one of the most researched (and effective) ways to boost levels.
• Your meat intake, exercise routine, muscle mass, and hormones (including testosterone and IGF-1) can all affect your stores [3].

What is creatine monohydrate?

 

Creatine monohydrate is the most common and well-researched form of creatine. It’s made by combining creatine with a water molecule and is known for being highly effective, affordable, and safe.

It comes as a powder, capsule, gummy, or chewable tablet. A standard dose is 3–5g per day, either with or without a loading phase.

 

Creatine monohydrate side effects – is it safe?

Creatine monohydrate is considered safe for most people. It’s been studied for decades and is backed by robust evidence showing both safety and effectiveness.

Having said that, some people may experience:

• Temporary water retention (due to increased muscle hydration)
• Bloating or mild stomach discomfort
• Weight gain (usually from added water in the muscles)

If you have pre-existing kidney issues, it’s wise to check with a doctor first.

 

What’s in creatine supplements?

 

Pure creatine monohydrate usually contains just one ingredient: creatine. This makes these dietary supplements suitable for most people, including vegetarians and vegans (always check the label to be sure it’s not derived from animal products).

Some supplements may contain:

• Carbohydrates (to aid absorption)
• Electrolytes
• Flavourings or other performance ingredients

Look for products with clear, minimal ingredient lists if you’re after a clean and simple option.

Now for the really technical part.

 

How do supplements work?

 

When you take a supplement, it binds to a phosphate group to form phosphocreatine, which supports the production of ATP (adenosine triphosphate) – the primary energy currency in your cells.

During intense exercise, ATP is rapidly broken down to produce energy, becoming ADP (adenosine diphosphate). Phosphocreatine recycles ADP back into ATP, allowing you to train harder and for longer [3].

Because phosphocreatine is also stored in the brain, these supplements may support brain health and cognitive function, especially under stress or fatigue [4–6].

 

What to look for in a supplement

 

Look for creatine monohydrate, the most studied and effective form. It’s widely available, cost-effective, and well absorbed by the body.

Key tips:

• Stick to 3–5g per day for maintenance
• Choose micronised creatine if you experience bloating
• Most powders are vegan-friendly and tasteless, so they are easy to mix into shakes or water

 

Three key benefits

1. Supports muscle growth

Creatine helps you train harder by increasing ATP availability, which increases muscle mass over time. 

Here's how:

• Increased training volume: More energy for lifting means more effective workouts [7]
• Cell hydration: Creatine pulls water into muscle cells, which may trigger anabolic (growth-promoting) pathways [8,9]
• Reduced myostatin: This protein limits muscle growth; creatine may lower its levels and unlock more growth potential [10]

Good to know:

A 14-week study on older adults found significant increases in leg strength and muscle mass with creatine supplementation during resistance training [12]. Another study found 2–3x greater muscle fibre growth in lifters who used creatine versus training alone [13].

2. Improves strength and performance

During short bursts of high-intensity activity, your ATP stores deplete in about 10 seconds. Creatine helps replenish them, extending performance and improving output [14,15].

In one study, participants who supplemented experienced:

• 7% increase in overall strength
• 14% improvement in lifting performance
• 43% increase in one-rep max bench press compared to training alone [16]

Another study found that trained athletes taking creatine for 28 days improved:

• Bike-sprint performance by 15%
• Bench press performance by 6% [16]

3. Enhances brain function

Because your brain also uses ATP, creatine may support cognitive health, particularly in situations where energy demand is high.

Research shows it may benefit:

• Alzheimer’s disease and neurodegeneration [17,18]
• Brain injuries – a 6-month study in children with traumatic brain injury found it reduced fatigue by 70% and dizziness by 50% [20]
• Memory and intelligence – vegetarians saw a 50% improvement in memory and a 20% boost in reasoning skills after supplementation [5]

Is creatine safe?

 

Creatine is one of the most thoroughly studied supplements available. A long-term study looking at 52 blood health markers over 21 months found no adverse effects from regular use [21].

Common concerns like dehydration, muscle cramps, or kidney stress are not supported by evidence. In fact, studies suggest it may reduce cramps and support hydration during exercise in the heat [22].

Side effects like stomach upset typically occur only if too much is taken at once or on an empty stomach.

Can creatine affect male fertility?

There’s no evidence that it harms male fertility. In fact, early research suggests it may support mitochondrial function in sperm, which could theoretically help (though more studies are needed to confirm this!).

As with any supplement, speak to your doctor or a fertility specialist if you’re actively trying to conceive and want personalised advice.

 

Creatine and your blood test results

 

If you’re training hard or taking creatine, you might see changes in your blood test results. And that’s not always a bad thing. For example, creatinine levels can rise with creatine supplements or higher muscle mass, it’s a natural by-product as it breaks down.

Hormones like testosterone, nutrients like vitamin B12 and iron, and stress markers like cortisol all play a role in performance, energy, and recovery and can influence or be influenced by your training and supplement routine.

 

 

What is the difference between creatine, creatinine, and CK?
 

Creatine kinase (CK) is an enzyme found throughout the body, but what can it tell you about your muscle health? Read our CK blog to find out more. 

 

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References

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2. Kreider, R. (2003). Effects of creatine supplementation on performance and training adaptations. Mol Cell Biochem, 244(1-2).
3. Persky, A. and Brazeau, A. (2001). Clinical pharmacology of the dietary supplement creatine monohydrate. Pharmacol Rev, 53(2), pp.161-76.
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5. Rae, C., Digney, A., McEwan, S. and Bates, T. (2003). Oral creatine monohydrate supplementation improves brain performance: a double–blind, placebo–controlled, cross–over trial. Proceedings of the Royal Society of London. Series B: Biological Sciences, 270(1529), pp.2147-2150.
6. Dechent, P., Pouwels, P., Wilken, B., Hanefeld, F. and Frahm, J. (1999). Increase of total creatine in human brain after oral supplementation of creatine-monohydrate. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 277(3), pp.R698-R704.
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13. Greenhaff, P., Bodin, K., Soderlund, K. and Hultman, E. (1994). Effect of oral creatine supplementation on skeletal muscle phosphocreatine resynthesis. American Journal of Physiology-Endocrinology and Metabolism, 266(5), pp.E725-E730.
14. Harris, R., Söderlund, K. and Hultman, E. (1992). Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation. Clinical Science, 83(3), pp.367-374.
15. Rawson, E. and Volek, J. (2003). Effects of Creatine Supplementation and Resistance Training on Muscle Strength and Weightlifting Performance. The Journal of Strength and Conditioning Research, 17(4), p.822.
16. Earnest, C., Snell, P., Rodriguez, R., Almada, A. and Mitchell, T. (1995). The effect of creatine monohydrate ingestion on anaerobic power indices, muscular strength and body composition. Acta Physiologica Scandinavica, 153(2), pp.207-209.
17. Kaemmerer, W., Rodrigues, C., J. Steer, C. and Low, W. (2001). Creatine-supplemented diet extends Purkinje cell survival in spinocerebellar ataxia type 1 transgenic mice but does not prevent the ataxic phenotype. Neuroscience, 103(3), pp.713-724.
18. Bürklen, T., Schlattner, U., Homayouni, R., Gough, K., Rak, M., Szeghalmi, A. and Wallimann, T. (2006). The Creatine Kinase/Creatine Connection to Alzheimer's Disease: CK Inactivation, APP-CK Complexes and Focal Creatine Deposits. Journal of Biomedicine and Biotechnology, 2006, pp.1-11.
19. McMorris, T., Mielcarz, G., Harris, R., Swain, J. and Howard, A. (2007). Creatine Supplementation and Cognitive Performance in Elderly Individuals. Aging, Neuropsychology, and Cognition, 14(5), pp.517-528.
20. Sakellaris, G., Nasis, G., Kotsiou, M., Tamiolaki, M., Charissis, G. and Evangeliou, A. (2007). Prevention of traumatic headache, dizziness and fatigue with creatine administration. A pilot study. Acta Paediatrica, 97(1), pp.31-34.
21. Kreider, B., Melton, C., Rasmussen, J., Greenwood, M., Lancaster, S., Cantler, C., Milnor, P. and Almada, A. (2003). Long-term creatine supplementation does not significantly affect clinical markers of health in athletes. Mol Cell Biochem, 244(2), pp.95-104.
22. Greenwood, M., Kreider, R., Melton, C., Rasmussen, C., Lancaster, S., Cantler, E., Milnor, P. and Almada, A. (2003). Creatine supplementation during college football training does not increase the incidence of cramping or injury. Mol Cell Biochem, 244(2), pp.83-8